flutter: expansionpanel does not close - flutter

Question

One expansion panel was expanded, and when the other expansion panel was expanded, the previous expanded one was set to be closed.
For example, when panel 1 is expanded and panel 2 is clicked, panel 1 is closed and panel 2 is expanded.
By the way, I tried to close panel 1 after expanding panel 1, but it didn't close.
How should I solve this?
class _RecordState extends State<Record> {
#override
void initState() {
super.initState();
}
int? _activeMeterIndex;
#override
void dispose() {
super.dispose();
}
#override
Widget build(BuildContext context) {
return Container(
child: new ListView.builder(
itemCount: 2,
itemBuilder: (BuildContext context, int i) {
return Card(
margin:
const EdgeInsets.fromLTRB(10.0, 15.0, 10.0, 0.0),
child: new ExpansionPanelList(
expansionCallback: (int index, bool status) {
setState(() {
_activeMeterIndex = (_activeMeterIndex == i ? _activeMeterIndex : i);
});
},
children: [
new ExpansionPanel(
isExpanded: _activeMeterIndex == i,
headerBuilder: (BuildContext context,
bool isExpanded) =>
new Container(
padding:
const EdgeInsets.only(left: 15.0),
alignment: Alignment.centerLeft,
child: new Text(
'list-$i',
)),
body: new Container(child: new Text('content-$i'),),
),
],
),
);
}),
);
}

Answer 1

you got the issue for the isExpanded: _activeMeterIndex == i, you must be used a unique index for each expansion tile and The callback gets called whenever one of the expand/collapse buttons is pressed. The arguments passed to the callback are the index of the pressed panel and whether the panel is currently expanded or not.
List<bool> _isExpand = [false, false,];
new ExpansionPanel(
isExpanded: _isExpand[i],
headerBuilder: (BuildContext context,
bool isExpanded) =>
new Container(
padding:
const EdgeInsets.only(left: 15.0),
alignment: Alignment.centerLeft,
child: new Text(
'list-$i',
)),
body: new Container(child: new Text('content-$i'),),
),
// callback
expansionCallback: (int index, bool status) {
setState(() {
_isExpand[i] = !status;
});
},